PUB - Publikationen an der Universität Bielefeld

Here we present functional and biochemical evidence for a Ca2+ channel (CaV1.2) /protein kinase C (PKC) signaling complex being a key player in muscarinic regulation of urinary bladder smooth muscle. Muscarinic stimulation induced Ca2+ signals and concomitant contractions in detrusor muscle from mice that were dependent on functional Ca2+ channels. These signals were still present in muscles being depolarized by 85 mM extracellular K+. Muscarinic-induced contractions were reduced by a PKC inhibitor [bisindolylmaleimide I (BIM-I)] and a phospholipase D (PLD) inhibitor (1-butanol). A phorbol ester (PDBu) enlarged muscarinic-induced Ca2+ signals and contractions. The effects of BIM-I and PDBu were inhibited by isradipine and/or absent in muscles from CaV1.2-deficient mice. Both carbachol and PDBu increased CaV1.2 channel currents in isolated bladder myocytes. Blue native-PAGE electrophoresis revealed that CaV1.2, PKC, and PLD are closely associated in muscles being previously stimulated by carbachol. Immunoprecipitation using anti-CaV1.2 followed by Western blotting demonstrated that CaV1.2 and PKC are coupled in stimulated muscles from wild-type mice. Autoradiography on immunoprecipitates showed that CaV1.2 is a substrate for PKC-mediated phosphorylation. These findings suggest that a signaling complex consisting of CaV1.2, PKC, and, probably, PLD controls muscarinic-mediated phasic contraction of urinary bladder smooth muscle.—Huster, M., Frei, E., Hofmann, F., Wegener, J. W. A complex of CaV1.2/PKC is involved in muscarinic signaling in smooth muscle. FASEB J. 24, 2651–2659 (2010).